Spark plug electrode



Patented Apr. 3, 1934 UNITED STATES PATENT OFFICE SPARK PLUG ELECTRODE No Drawing. Original application May 1, 1931,

Serial No. 534,463. Divided and this application December 9, 1933, Serial No. 701,729

5 Claims.

This invention relates to spark plug electrodes, the present application being a division of my prior application Serial No. 534,463, filed May 1, 1931, and entitled Spark plug electrodes.

When an electric current is passed to or from a spark plug electrode of an internal combustion engine or the like, a disintegration of the electrode occurs resulting in time in completely destroying the material thereof. A spark plug elec- 1. trode is subjected not only to high temperatures but also to the action of chemical and physical agencies, this effect being particularly noticeable and objectionable when tetra-ethyl lead is used in the gasoline forming a charge. The corrosion and erosion caused in the highly heated atmosphere surrounding the electrode by metallic lead, lead oxides, halogen lead compounds, halogen acids, and sulfur or sulfur compounds is very great. The rapid flow of the gas carrying these compounds increases the rate of deterioration. Also the acid products of combustion or the acid products produced by the hydrolysis of combustion deposits readily attack the electrode both in the zone of the arc, and outside thereof to further disintegrate the same. 7

It is an object of the present invention to provide an electrode which will to a great extent overcome the defects and disadvantages mentioned, and which can withstand high temperatures without deterioration.

It is a further object to provide a spark plug electrode which will resist the corrosion and erosion produced by modern fuels embodying tetra-ethyl lead.

It is a. further object to provide an improved spark plug that is simple and inexpensive to man-- ufacture and which has a long period of usefulness without requiring replacement or readjustment.

The material which, according to the present invention, is used for forming a spark plug electrode that is adapted to resist the deteriorating effects of corrosion and erosion comprises a ferrous base and certain additive materials, one of which is chromium.

Chromium should be present in amounts varying from approximately 6% to 18%. These and other percentages are given as illustrative of the preferred range of the several elements only, and it will be understood that the limits may be extended somewhat and the resulting alloy will still retain substantially the desired corrosion resisting properties. Chromium and iron alone do not produce a satisfactory material for spark plug electrodes: but certain additional sion and erosion resisting. As one example of this material, aluminum may be added, varying in amounts from 2% to 10%. In addition if desired, silicon up to 4% is employed.

One composition which has been found to give very satisfactory results consists of a ferrous base alloy having, in addition to the chromium, 2% to 10% aluminum and 3% to 6% silicon. The composition of one such material is 6% to 13% chromium, 7% to 10% aluminum, 3% to 6% slli-= con and the remainder iron.

Numerous tests have demonstrated that electrodes formed of the compositions set forth above have greatly increased corrosion and erosion resisting properties, and are particularly adapted for use with ethyl gasoline which has little deteriorating effect upon such electrodes. Where other electrode materials become coated with oxide andscale, and even disintegrate under the conditions obtaining in the cylinder of an internal combustion engine, the materials of the present invention remain clear, smooth and practically uncoated over very long periods .of use. They offer greatly improved resistance to erosion by the electric arc with current values employed in ignition circuits when the atmosphere surrounding the electrode contains metallic lead, lead oxides, halogen lead compounds, halogen acids, and free sulfur or sulfur compounds. The reduced rate of erosion may be due, in part, to a reduction in the eating away of the opposed electrode surfaces between which the arc passes as a result of improved resistance to condensed acid product of combustion of gasoline or acid products produced by the hydrolysis of deposits resulting from combustion. By means of the composition of this invention,

he construction of spark plugs can be greatly simplified and the cost reduced while at the same time their period of life may be extended. As now constructed spark plugs ordinarily are made up of a core electrode, a core spindle, and a core spindle head, of different metals. By using a material of the present invention for all these parts or for the core electrode and either of the other parts, the entire core structure may be simplified and made integral without increasing the cost of the spark plug. Similarly, the shell, which nowordinarily is made of one metal and the side electrode of another, may also be made entirely of this inexpensive material with a consequent reduction in the manufacturing cost. Heretofore such alloys as have been suitable for electrodes have been so expensive as to prohibit their use for forming the entire spark plug structure there from. The present invention provides a material extremely resistant to corrosion and erosion which at the same time is relatively inexpensive so that all of the parts of the spark plug may be constructed thereof and the usual expense of assembling the several portions of shell and core eliminated.

While the materials herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise compositions, and that changes may be made therein Without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A spark plug electrode having improved corrosion and erosion resistance to condensed acid products of combustion of gasoline comprising a, ferrous base alloy containing 6% to 18% chromium and 2% to 10% aluminum.

2. A spark plug electrode adapted to resist corrosion and having improved resistance to emsion by the electric are when the atmosphere surrounding the electrode contains lead, lead compounds, halogen compounds or sulfur comprising a ferrous base alloy having 6% to 18% chromium, 2% to 10% aluminum and silicon in amounts not over 6%.

3. A spark plug electrode adapted to resist cor rosion and erosion comprising a ferrous base alloy having 6% to 13% chromium, 2% to 10% alu 

